As already said above, these are a bastard to start when there is air in the system (due to fuel filter being replaced) I use a hand primer and link it to the fuel line after the filter to draw fuel through the filter and start it with the hand primer still in place. These tdci's have lots of faults, I have seen them throwing up fuel pressure faults etc when its a faulty cam sensor, if you have no luck I would take it to someone who deals with them all the time, they will prob sort it out in no time